Benefit Plans (Schedule Of Components Of Net Periodic Benefit Cost (Income)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Amortization:
Net periodic benefit cost (income)	$ (7)	$ (8)
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	21	19
Interest cost	68	72
Expected return on plan assets	(146)	(150)
Amortization:
Net loss	57	50
Prior service cost (credit)	1	1
Net periodic benefit cost (income)	1	(8)
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4
Interest cost	19	20
Expected return on plan assets	(5)	0
Amortization:
Net loss	9	8
Prior service cost (credit)	(10)	(9)
Net periodic benefit cost (income)	$ 17	$ 23